Two-photon-excited fluorescence spectroscopy of Rb atoms in a magneto-optical trap

arXiv:2602.07161v1 Announce Type: new
Abstract: We report the results of two-photon-excited fluorescence (TPEF) measurements of the $5mathrm{S}_{1/2} rightarrow 5mathrm{D}_{1/2}$ transition of $^{85}$Rb and $^{87}$Rb cooled in a magneto-optical trap (MOT). We observe TPEF at excitation powers as low as 1 $mu$W or fluxes as low as $4.30 pm 0.22 times 10^{18} text{photons},text{cm}^{-2},text{s}^{-1}$ ($^{85}$Rb) and $5.17 pm 0.26 times 10^{18} text{photons},text{cm}^{-2},text{s}^{-1}$ ($^{87}$Rb). Our results show that Rb, with additional benefits due to its ability to be optically cooled to the point where Doppler-broadening is negligible, is a promising platform for observing sensitive two-photon spectral signatures at low photon fluxes.